I like to alternate my mileage and pacing for variety. Every week I like to do a long slow run (6 to 8 miles), two 3 mile runs at a quick pace, a four or five miler with a lot of elevation, and a one miler at a very quick pace. So each run takes anywhere from 2 hours to 30 minutes, with stretching and cool down walking. Of course a lot of this just depends on what you prefer. I like to run in the afternoon after work, while many people enjoy running in the morning or only have time in the morning. Some people prefer to run by time, not distance. And some prefer to run the same distance everyday. Find what works for you! EDIT: I use a website called RunMyRoute to map out my routes and mileage. Or if you prefer to run by time, I'd say just approximate how long it takes you to run a mile and just multiply that by how many miles you want run. Take an extra 15-20 minutes for warm up/stretching/cool down.